On Wed, Sep 16, 2015 at 10:02:00PM -0700, Cong Wang wrote:
>
> This part doesn't look correct, seems it is checking if this is a kernel
> netlink socket rather than if it is bound. But I am not sure...
Good point. I've changed it so that bound is only set for non-kernel
sockets.
---8<---
netlink: Fix autobind race condition that leads to zero port ID
The commit c0bb07df7d981e4091432754e30c9c720e2c0c78 ("netlink:
Reset portid after netlink_insert failure") introduced a race
condition where if two threads tried to autobind the same socket
one of them may end up with a zero port ID.
This patch reverts that commit and instead fixes it by introducing
a separte "bound" variable to indicate whether a user-space socket
has been bound.
Fixes: c0bb07df7d98 ("netlink: Reset portid after netlink_insert failure")
Reported-by: Tejun Heo <t...@kernel.org>
Reported-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Herbert Xu <herb...@gondor.apana.org.au>
Reviewed-by: Cong Wang <cw...@twopensource.com>
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index dea9253..42013c5 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1068,7 +1068,7 @@ static int netlink_insert(struct sock *sk, u32 portid)
lock_sock(sk);
err = -EBUSY;
- if (nlk_sk(sk)->portid)
+ if (nlk_sk(sk)->bound)
goto err;
err = -ENOMEM;
@@ -1083,10 +1083,12 @@ static int netlink_insert(struct sock *sk, u32 portid)
if (err) {
if (err == -EEXIST)
err = -EADDRINUSE;
- nlk_sk(sk)->portid = 0;
sock_put(sk);
+ goto err;
}
+ nlk_sk(sk)->bound = !!portid;
+
err:
release_sock(sk);
return err;
@@ -1253,7 +1255,7 @@ static int netlink_release(struct socket *sock)
skb_queue_purge(&sk->sk_write_queue);
- if (nlk->portid) {
+ if (nlk->bound) {
struct netlink_notify n = {
.net = sock_net(sk),
.protocol = sk->sk_protocol,
@@ -1487,7 +1489,7 @@ static int netlink_bind(struct socket *sock, struct
sockaddr *addr,
return err;
}
- if (nlk->portid)
+ if (nlk->bound)
if (nladdr->nl_pid != nlk->portid)
return -EINVAL;
@@ -1505,7 +1507,7 @@ static int netlink_bind(struct socket *sock, struct
sockaddr *addr,
}
}
- if (!nlk->portid) {
+ if (!nlk->bound) {
err = nladdr->nl_pid ?
netlink_insert(sk, nladdr->nl_pid) :
netlink_autobind(sock);
@@ -1553,7 +1555,7 @@ static int netlink_connect(struct socket *sock, struct
sockaddr *addr,
!netlink_allowed(sock, NL_CFG_F_NONROOT_SEND))
return -EPERM;
- if (!nlk->portid)
+ if (!nlk->bound)
err = netlink_autobind(sock);
if (err == 0) {
@@ -2371,7 +2373,7 @@ static int netlink_sendmsg(struct socket *sock, struct
msghdr *msg, size_t len)
dst_group = nlk->dst_group;
}
- if (!nlk->portid) {
+ if (!nlk->bound) {
err = netlink_autobind(sock);
if (err)
goto out;
diff --git a/net/netlink/af_netlink.h b/net/netlink/af_netlink.h
index 8900840..e6aae40 100644
--- a/net/netlink/af_netlink.h
+++ b/net/netlink/af_netlink.h
@@ -35,6 +35,7 @@ struct netlink_sock {
unsigned long state;
size_t max_recvmsg_len;
wait_queue_head_t wait;
+ bool bound;
bool cb_running;
struct netlink_callback cb;
struct mutex *cb_mutex;
--
Email: Herbert Xu <herb...@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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